This invention relates to the attachment of railroad grade crossing elements to railroad ties, and in particular to the attachment of rubber grade crossing elements to concrete ties.
Whenever a roadway crosses a railroad track, a grade crossing must be installed to bring the space above the ties up to the level of rails. In the past when both the grade crossing elements and ties were wood this was easily accomplished by driving spikes through the grade crossing elements into the underlying ties. Now that railroad ties are made of concrete this method of attaching the grade crossing elements to them no longer is possible.
While lag bolts and expandable anchors can be used for this purpose, drilling the holes necessary for the anchors is a time-consuming and costly process. In addition, since concrete ties are pre-stressed, any holes drilled in them have to be carefully placed and drilled to keep from reducing the strength of the tie. Accordingly, using anchors and bolts to attach grade crossing elements to concrete ties is extremely expensive.
Another method for attaching grade crossing elements to concrete ties is to bond them together with a high-strength adhesive. This has two problems associated with it, however. One problem is that many concrete ties have concave indentations in their top surfaces between the rails, in order to reduce the material cost and the weight of the ties. In addition, these indentations have different shapes in ties made by different manufacturers. Thus, filler pads must be bonded to each tie before the crossing element can be adhered to it. This increases the labor cost of attaching the grade crossing as well as possibly interrupting the attachment process while the adhesive used to bond the filler pad dries. A greater difficulty with adhesively bonding crossing elements to ties is that the concrete ties and rubber crossing elements now in use are extremely long-lived. Accordingly, it is necessary to remove the crossing elements from the ties occasionally to retamp the bed the railroad is constructed on, and then to reattach the crossing elements to the ties. This cannot easily be accomplished when the crossing elements are adhesively bonded to the ties in the first instance.
What is needed, therefore, is a tie-down system which allows any type of railroad grade crossing elements to be attached to any type of railroad ties in a manner which permits them to easily be removed and then reinstalled.
This is accomplished in the present invention by attaching anchor plates to the top surfaces of the ties by mechanical fasteners or an adhesive, depending upon the material the ties and anchor plates are constructed from. The anchor plates substantially cover the entire length of the ties which do not have rails attached to them, and have a width which is greater than the width of the ties. Thus the anchor plates have side margins which extend outwardly from the sides of the ties. In addition, the bottoms of the anchor plates can be contoured to fill any cavities which are formed in the tops of the ties, thereby allowing the cavities to be filled and the anchor plates attached in a single operation. Openings are placed in the crossing elements above the side margins of the anchor plates, and clamps, which are attached to the crossing elements and extend under the side margins of the anchor plates, can be tightened from above through these openings to squeeze the side margins between the crossing elements and the clamp.
In a preferred embodiment of the invention, the openings are centered between adjacent ties and the clamp includes an elongate cross tie beam which has a length that is slightly greater than the distance between adjacent ties. The cross tie beam has a lock nut fixedly attached to its center which engages a bolt that fits through an opening in a crossing element. The cross tie beam is attached loosely to the bolt and the cross tie beam is oriented parallel with the ties before the crossing element is placed on top of the anchor plates. Once the crossing element is in place the bolt is turned in a direction which would cause it to be threaded into the nut. When this occurs the cross tie beam will rotate with the bolt until its ends contact the sides of the ties. The cross tie beam then will become jammed and further tightening of the bolt will cause the cross tie beam to be drawn up toward the side margins of the anchor plates. When fully tightened the cross tie beam will engage the side margins of the anchor plates and clamp the crossing element to the anchor plates.
Accordingly, it is a principal object of the present invention to provide a system for attaching railroad grade crossing elements releasably to the ties which support them.
It is a further object of the present invention to provide such a system which will work for ties and crossing elements made from any type of material.
The foregoing and other objectives, features and advantages of the present invention will be more readily understood upon consideration of the following detailed description of the invention taken in conjunction with the accompanying drawings.